[FFmpeg-devel] [PATCH v2] avcodec/interplayvideo: Check sizes of decode buffers
Hein-Pieter van Braam
hp at tmm.cx
Mon Jul 3 12:56:14 EEST 2017
On Mon, 2017-07-03 at 11:43 +0200, Paul B Mahol wrote:
> On 7/2/17, Hein-Pieter van Braam <hp at tmm.cx> wrote:
> > Fixes: 6503 crash with fuzzed file
> > Signed-off-by: Hein-Pieter van Braam <hp at tmm.cx>
> > ---
> > libavcodec/interplayvideo.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> > diff --git a/libavcodec/interplayvideo.c
> > b/libavcodec/interplayvideo.c
> > index d6f484a..86530e6 100644
> > --- a/libavcodec/interplayvideo.c
> > +++ b/libavcodec/interplayvideo.c
> > @@ -972,6 +972,8 @@ static void
> > ipvideo_decode_format_06_opcodes(IpvideoContext *s, AVFrame *frame)
> > x, y, opcode, bytestream2_tell(&s-
> > >stream_ptr));
> > s->pixel_ptr = frame->data + x + y * frame-
> > >linesize;
> > + if (s->pixel_ptr > (s->pixel_ptr +
> > s->upper_motion_limit_offset))
> > + return;
> This looks strange.
The code already has a feature to ensure that movement vectors can't
write past the end of the target AVFrame. I thought I'd reuse this to
prevent writing past the end of the current AVFrame for the 'regular'
pixeldata too. This code checks the value of the pointer into the
AVFrame's pixeldata is not further than the last 8x8 block so that we
can't write past it.
Would there be a better way of doing this?
Although, I suppose if I check the size of the AVFrame itself instead
then it would also be safe because of the for loop. I can also
implement it like that if that's preferred?
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